Control apparatus for vehicle

ABSTRACT

A control apparatus for a vehicle is provided for a vehicle that has a normal mode and a power mode as vehicle driving characteristics. The control apparatus includes a continuously variable transmission mechanism that steplessly changes a speed ratio when rotational driving force of an engine output shaft is transmitted to a rotating output shaft; and a control portion that controls the continuously variable transmission mechanism such that, when a rotation speed is increased to a target rotation speed and a required output of an internal combustion engine when the power mode is selected is the same as when the normal mode is selected, the rate of increase in the rotation speed is greater when the power mode is selected than when the normal mode is selected.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a control apparatus for a vehicle that isapplied to a vehicle in which rotational driving force of an engineoutput shaft that is an output shaft of an internal combustion engine istransmitted to driving wheels via a rotating output shaft, and that hasa normal mode and a power mode as vehicle driving characteristics.

2. Description of the Related Art

Japanese Patent Application Publication No. 2007-091073(JP-A-2007-091073), for example, describes one such known controlapparatus for a vehicle. One kind of typical related control apparatusfor a vehicle, including that described in JP-A-2007-091073, has anormal mode and a power mode as vehicle driving characteristics in orderto meet the high requirements of the driver for driving force. Thiscontrol apparatus changes the vehicle driving characteristic by changingthe output characteristic of the internal combustion engine according tothe mode selected. More specifically, the opening amount of the throttlevalve with respect to the accelerator operation amount is controlled tobe larger when the power mode is selected than it is when the normalmode is selected. This kind of control enables a greater feeling ofacceleration to be obtained when the power mode is selected than isobtained when the normal mode is selected.

In the related control apparatus for a vehicle described above, thevehicle driving characteristic is changed by changing the controlcharacteristic of the opening amount of the throttle valve with respectto the accelerator operation amount so that it is different for thenormal mode than it is for the power mode. Therefore, when the vehicleis accelerating with the accelerator pedal fully depressed, thefollowing problem may arise. When the accelerator pedal is fullydepressed, the throttle becomes fully open as a result, so the requiredoutput of the internal combustion engine is the same when the power modeis selected as it is when the normal mode is selected. In this case, theopening amount of the throttle valve is unable to be increased any morewith respect to the accelerator operation amount. Therefore, even thoughthe power mode is selected, a greater feeling of acceleration than whenthe normal mode is selected is unable to be obtained.

SUMMARY OF THE INVENTION

This invention thus provides a control apparatus for a vehicle thatenables a greater feeling of acceleration to be obtained when a powermode is selected than when a normal mode is selected, even if therequired output of an internal combustion engine is the same when thepower mode is selected as it is when the normal mode is selected.

One aspect of the invention relates to a control apparatus for avehicle, the vehicle being structured such that rotational driving forceof an engine output shaft that is an output shaft of an internalcombustion engine is transmitted to a driving wheel via a rotatingoutput shaft, and having a normal mode and a power mode as vehicledriving characteristics. This control apparatus includes a continuouslyvariable transmission mechanism that steplessly changes a speed ratiowhen the rotational driving force of the engine output shaft istransmitted to the rotating output shaft, and a control portion thatcontrols the continuously variable transmission mechanism such that,when a rotation speed of the engine output shaft is increased to atarget rotation speed and a required output of the internal combustionengine when the power mode is selected is the same as when the normalmode is selected, the rate of increase in the rotation speed of theengine output shaft is greater when the power mode is selected than whenthe normal mode is selected.

According to this aspect of the invention, when the required output ofthe internal combustion engine is the same when the power mode isselected as it is when the normal mode is selected, the rate of increaseof the rotation speed of the engine output shaft is made larger bycontrolling the continuously variable transmission mechanism when thepower mode is selected than it is when the normal mode is selected. Thiskind of control enables the rotation speed of the engine output shaft tobe quickly increased to the target rotation speed. Increasing thepercentage of output from the internal combustion engine thatcontributes to the increase in the rotation speed of the engine outputshaft in this way results in a decrease in the percentage of output fromthe internal combustion engine that contributes to an increase indriving force transmitted to the rotating output shaft, and thus adecrease in the acceleration of the vehicle until the rotation speed ofthe engine output shaft reaches the target rotation speed. However, oncethe rotation speed of the engine output shaft has reached to the targetrotation speed, the majority of the output from the internal combustionengine is contributed to increasing the driving force transmitted to therotating output shaft, so the acceleration of the vehicle abruptlyincreases. Therefore, the acceleration of the vehicle can be quicklyincreased to a predetermined acceleration. Also, the rate of increasewhen increasing the acceleration of the vehicle, i.e., the so-calledjerk, is able to be made large. Therefore, a greater feeling ofacceleration can be obtained when the power mode is selected than whenthe normal mode is selected, even if the required output of the internalcombustion engine is the same when the power mode is selected as it iswhen the normal mode is selected.

In the aspect of the invention described above, the vehicle may be suchthat a throttle valve of the internal combustion engine is fully openwhen an accelerator operation amount is substantially equal to themaximum amount. Also, when the rotation speed of the engine output shaftis increased to the target rotation speed when the accelerator operationamount is substantially equal to the maximum amount, the control portionmay control the continuously variable transmission mechanism such thatthe rate of increase of the rotation speed of the engine output shaft isgreater when the power mode is selected than when the normal mode isselected. In a vehicle in which the throttle valve is fully open whenaccelerator operation amount is substantially equal to the maximumamount, the required output of the internal combustion engine is thesame when the accelerator operation amount is substantially equal to themaximum amount. Therefore, if this aspect of the invention is appliedwhen a vehicle is accelerating with the accelerator operation amountbeing substantially equal to the maximum amount, a greater feeling ofacceleration can be obtained when the power mode is selected than whenthe normal mode is selected.

In the control apparatus described above, when the rotation speed of theengine output shaft is increased to the target rotation speed when thepower mode is selected, the control portion may control the continuouslyvariable transmission mechanism such that the driving force transmittedto the rotating output shaft, of the output from the internal combustionengine, decreases.

According to this structure, when the rotation speed of the engineoutput shaft is increased to the target rotation speed when the powermode is selected, the output of the internal combustion engine thatcontributes to an increase of the rotation speed of the engine outputshaft increases by the amount that the driving force transmitted to therotating output shaft, of the output of the internal combustion engine,decreases. Therefore, the rotation speed of the engine output shaft canbe increased to the target rotation speed even more quickly, whichenables the acceleration of the vehicle to be increased even morequickly to a predetermined acceleration. Also, the jerk of the vehiclecan be made large. Therefore, an even greater feeling of accelerationcan be obtained when the power mode is selected than when the normalmode is selected, even if the required output of the internal combustionengine is the same when the power mode is selected as it is when thenormal mode is selected.

In the control apparatus described above, when the rotation speed of theengine output shaft is increased to the target rotation speed when thenormal mode is selected, the control portion may control thecontinuously variable transmission mechanism such that the driving forcetransmitted to the rotating output shaft, of the output from theinternal combustion engine, increases. Incidentally, in combination withthis, when the power mode is selected, for example, the control portionmay control the continuously variable transmission mechanism such thatthe driving force transmitted to the rotating output shaft, of theoutput from the internal combustion engine, increases until the rotationspeed of the engine output shaft reaches the target rotation speed.However, in this case as well, it is necessary to increase the rate ofincrease when increasing the rotation speed of the engine output shaftto the target rotation speed when the power mode is selected comparedwith when the normal mode is selected.

In the control apparatus described above, the control portion may reducethe rate of increase of the rotation speed of the engine output shaftafter the rotation speed of the engine output shaft has been increasedto a predetermined rotation speed that is lower than the target rotationspeed, and set the predetermined rotation speed higher when the powermode is selected than when the normal mode is selected.

If the rotation speed of the engine output shaft is abruptly stoppedfrom increasing after it has increased to the target rotation speed, thesudden change in acceleration of the engine rotation speed will joltparts of the internal combustion engine, which may result in mechanicaldamage to the internal combustion engine. Therefore, the rate ofincrease of the rotation speed of the engine output shaft after therotation speed of the engine output shaft has increased to apredetermined rotation speed that is lower than the target rotationspeed is reduced to inhibit the internal combustion engine from beingmechanically damaged. According to this structure, the rotation speed ofthe engine output shaft can be increased even more quickly to the targetrotation speed by setting the predetermined rotation speed for reducingthe rate of increase of the rotation speed of the engine output shafthigher when the power mode is selected than when the normal mode isselected. As a result, the acceleration of the vehicle can be increasedto a predetermined acceleration even more quickly, and the jerk of thevehicle can be made even larger.

The control apparatus described above may also include a hybrid powersystem that has a generator; an output splitting mechanism thatdistributes a portion of the output from the internal combustion engineto the rotating output shaft and distributes the rest of the output fromthe internal combustion engine to the generator; a power storage devicethat is charged with the electric power generated by the generator; andan electric motor that is driven by at least one of the electric powerfrom the generator or the electric power from the power storage device,and transmits power to the rotating output shaft. Also, the continuouslyvariable transmission mechanism may steplessly change the speed ratiowhen the rotational driving force of the engine output shaft istransmitted to the rotating output shaft, by operational control of thegenerator.

According to the structure described above, the speed ratio when therotational driving force of the engine output shaft is transmitted tothe rotating output shaft can easily be changed by controlling theoperation of the generator.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of theinvention will become apparent from the following description of exampleembodiments with reference to the accompanying drawings, wherein likenumerals are used to represent like elements and wherein:

FIG. 1 is a block diagram schematically showing the general structure ofa hybrid drive system that serves as the power system of a vehicle in anexample embodiment of a control apparatus for a vehicle according to theinvention;

FIG. 2A is an alignment graph of a planetary gear set, and FIG. 2B is analignment graph of a transmission;

FIG. 3 is a map that defines the relationship between acceleratoroperation amount and throttle opening amount;

FIG. 4 is a flowchart illustrating a routine for setting the parametersin this example embodiment; and

FIGS. 5A to 5E are timing charts illustrating the operation of thisexample embodiment, with FIG. 5A being a timing chart showing the shiftin accelerator operation amount, FIG. 5B being a timing chart showingthe shift in the throttle opening amount, FIG. 5C being a timing chartshowing the shift in the accelerator torque of a MG1, FIG. 5D being atiming chart showing the shift in the engine speed, and FIG. 5E being atiming chart showing the shift in acceleration of the vehicle.

DETAILED DESCRIPTION OF EMBODIMENTS

An example embodiment of the control apparatus for a vehicle accordingto the invention will now be described in detail with reference to FIGS.1 to 5E. Incidentally, the vehicle in this example embodiment isprovided with a hybrid power system 2 that serves as the power system ofthe vehicle.

FIG. 1 is a block diagram showing the general structure of the hybridpower system 2. As shown in the drawing, in the hybrid power system 2,torque output from a main power source 4 is transmitted to a rotatingoutput shaft 6, and then transmitted as driving force from the rotatingoutput shaft 6 to driving wheels 10 via a differential 8. Also, thishybrid power system 2 is provided with a motor-generator 12 (hereinaftersimply referred to as “MG2”) that is an assist power source in whichboth powering control to output driving force for running andregenerative control to recover energy are possible. The MG2 isconnected to the rotating output shaft 6 via a transmission 14. Torquetransmitted between the MG2 and the rotating output shaft 6 is increasedor decreased according to the speed ratio established in thetransmission 14.

The main power source 4 mainly includes an internal combustion engine16, a motor-generator 18 (hereinafter simply referred to as “MG1”), anda planetary gear set 20 that combines the torque from the internalcombustion engine 16 and the MG1 or splits the torque from the internalcombustion engine 16 between the MG1 and the driving wheels 10. Theinternal combustion engine 16 is a gasoline engine and is structuredsuch that the operating state, e.g., the opening amount of a throttlevalve 17 that adjusts the intake air amount, the amount of fuelsupplied, and the ignition timing, and the like, can be electricallycontrolled. This control is performed by an electronic control unit(E-ECU) 22 that includes a microcomputer as its main component.

The MG1 is a synchronous electric motor that can function both as anelectric motor and a generator, and is connected to a power storagedevice 26 via an inverter 24. The output, torque and regenerated torqueof the MG1 are set by controlling the inverter 24 using an electroniccontrol unit (MG-ECU) 28 that includes a microcomputer as its maincomponent. Incidentally, the MG1 and the planetary gear set 20 in thisexample embodiment together function as a continuously variabletransmission mechanism of the invention. That is, the speed ratio whenrotational driving force of a crankshaft 16 a is transmitted to therotating output shaft 6 is steplessly changed by controlling theoperation of the MG1 using the MG-ECU 28.

The MG2 is connected to the power storage device 26 via an inverter 29.Powering and regeneration, as well as the torque in both of these cases,are controlled by the MG-ECU 28 controlling the inverter 29.

The planetary gear set 20 is a gear mechanism that performs adifferential operation with three rotating elements, i.e., a sun gear 20a, a ring gear 20 b that is arranged concentric with the sun gear 20 a,and a carrier 20 c that rotatably and revolvably retains pinion gearsthat are in mesh with both the sun gear 20 a and the ring gear 20 b. Thecrankshaft 16 a that serves as the output shaft of the internalcombustion engine 16 is connected via a damper 16 b to the carrier 20 c,so the carrier 20 c serves as the input element.

The MG1 is connected to the sun gear 20 a, and this sun gear 20 a servesas the reaction force element. Therefore, the ring gear 20 b is theoutput element and is connected to the rotating output shaft 6. FIG. 2Ais an alignment graph of the planetary gear set 20 that functions as thetorque splitting mechanism described above (but can also function as atorque combining mechanism).

As shown in the drawing, the planetary gear set 20 is able to distributea portion of the power from the internal combustion engine 16 to therotating output shaft 6 and distribute the rest to the MG1. Thetransmission 14 is formed by a Ravigneaux type planetary gear set. Thatis, the transmission 14 has a first sun gear 14 a and a second sun gear14 b. A short pinion 14 c is in mesh with the first sun gear 14 a, andthat short pinion 14 c and the second sun gear 14 b are in mesh with along pinion 14 d that is longer in the axial direction than the shortpinion 14 c. A ring gear 14 e is arranged concentric with the sun gears14 a and 14 b, and is in mesh with the long pinion 14 d. The pinions 14c and 14 d are rotatably and revolvably retained by a carrier 14 f.Therefore, the first sun gear 14 a and the ring gear 14 e, together withthe pinions 14 c and 14 d, form a mechanism that corresponds to a doublepinion type planetary gear set. Also, the second sun gear 14 b and thering gear 14 e, together with the long pinion 14 d, form a mechanismthat corresponds to a single pinion type planetary gear set.

Further, the transmission 14 includes a first brake B1 that selectivelyholds the first sun gear 14 a against rotation, and a second brake B2that selectively holds the ring gear 14 e against rotation. These brakesB1 and B2 are formed such that their torque capacities continuouslychange according to the engaging force generated by hydraulic pressureor electromagnetic force or the like. Incidentally, hydraulic pressureis used in this example embodiment. The MG2 described above is connectedto the second sun gear 14 b, and the carrier 14 f is connected to therotating output shaft 6.

Therefore, the input element of the transmission 14 is the second sungear 14 b and the output element of the transmission 14 is the carrier14 f. In this transmission 14, a high speed in which a speed ratiosmaller than 1 is established by engaging the first brake B1, and a lowspeed in which the speed ratio is larger than the speed ratio of thehigh speed is established by engaging the second brake B2 instead of thefirst brake B1. A shift between these speeds is executed based on therunning state such as the vehicle speed SP and the required drivingforce (or the accelerator operation amount ACCP) and the like. Morespecifically, a speed range is set in the form of a map (i.e., a shiftline graph) beforehand, and control is performed to establish one ofthose two speeds depending on the detected operating state. This kind ofcontrol is performed by an electronic control unit (HV-ECU) 30 thatincludes a microcomputer as its main component.

FIG. 2B is an alignment graph of the transmission 14. As shown in thedrawing, when the ring gear 14 e is held stationary by the second brakeB2, the low speed is established such that the torque output from theMG2 is multiplied according to the speed ratio and then applied to therotating output shaft 6. When the first sun gear 14 a is held stationaryby the first brake B1, the high speed in which the speed ratio issmaller than it is in the low speed is established. The speed ratio ofthis high speed is also smaller than 1, so the torque output from theMG2 is increased according to that speed ratio and then applied to therotating output shaft 6.

In a state in which the high speed or the low speed is constantlyestablished, the torque that is applied to the rotating output shaft 6is the output torque of the MG2 after it has been increased according tothe speed ratio. Incidentally, the detection results from varioussensors that detect the operating state of the engine and the runningstate of the vehicle are input to the HV-ECU 30. Some examples of thesesensors include an accelerator operation amount sensor 31 that detectsthe accelerator operation amount ACCP which is the requirement ofdriving force by the driver, an engine speed sensor 16 c that detectsthe engine speed NE which is the rotation speed of the crankshaft 16 aof the internal combustion engine 16, a throttle opening amount sensor17 a that detects the opening amount of the throttle valve 17(hereinafter simply referred to as “throttle opening amount” TA), and avehicle speed sensor 6 a that detects the rotation speed of the rotatingoutput shaft 6, i.e., the vehicle speed SP. The E-ECU 22, the MG-ECU 28,and the HV-ECU 30 are all connected together so as to be able tocommunicate with one another.

Now, the vehicle in this example embodiment has a normal mode and apower mode as vehicle driving characteristics in order to meet the highrequirements of the driver for driving force. The vehicle drivingcharacteristic is changed by changing the output characteristic of theinternal combustion engine 16 according to the mode selected by thedriver. More specifically, as shown in FIG. 3, control is performed suchthat the throttle opening amount TA with respect to the acceleratoroperation amount ACCP is greater when the power mode is selected than itis when the normal mode is selected. This kind of control enables agreater feeling of acceleration to be obtained when the power mode isselected than is obtained when the normal mode is selected.Incidentally, the switch between the normal mode and the power mode isperformed by an operation of a switch, not shown, provided in thevehicle cabin. A signal from the switch is output to the HV-ECU 30.

In the control described above, the vehicle driving characteristic ischanged by changing the control characteristic of the throttle openingamount TA with respect to the accelerator operation amount ACCP so thatit is different for the normal mode from it is for the power mode.Therefore, a problem may arise when the vehicle is accelerating with theaccelerator operation amount ACCP at the maximum amount, for example.That is, when the accelerator operation amount ACCP at the maximumamount, the throttle opening amount TA is also the maximum amount as aresult, so the required output of the internal combustion engine 16 isthe same when the power mode is selected as it is when the normal modeis selected. In this case, the throttle opening amount TA is unable tobe increased any more with respect to the accelerator operation amountACCP. Therefore, even though the power mode is selected, a greaterfeeling of acceleration as compared to the feeling of acceleration whenthe normal mode is selected is unable to be obtained.

Thus, in this example embodiment, when the engine speed NE is increasedto a target speed NEtrg when the accelerator operation amount ACCP issubstantially equal to the maximum amount, the MG1 is controlled suchthat the rate of increase of the engine speed NE is greater when thepower mode is selected than it is when the normal mode is selected. Thiskind of control quickly increases the acceleration G of the vehicle to apredetermined acceleration, and thus increases the rate of increase whenthe acceleration G of the vehicle is increased, i.e., increases jerk J.As a result, a greater feeling of acceleration can be obtained when thepower mode is selected than can be obtained when the normal mode isselected, even when the accelerator operation amount ACCP issubstantially equal to the maximum amount.

Here, the reason why it is possible to quickly increase the accelerationG of the vehicle to a predetermined acceleration, and thus increase thejerk J of the vehicle, by increasing the rate of increase of the enginespeed NE will now be described. When the accelerator operation amountACCP is substantially equal to the maximum amount, i.e., when therequired power of the internal combustion engine 16 is the same when thepower mode is selected as it is when the normal mode is selected, theengine speed NE is quickly increased to the target speed NEtrg bycontrolling the MG1 such that the rate of increase of the engine speedNE becomes greater when the power mode is selected than when the normalmode is selected. Increasing the percentage of output from the internalcombustion engine 16 that contributes to an increase in engine speed NEin this way results in a decrease in the percentage of output from theinternal combustion engine 16 that contributes to an increase in drivingforce transmitted to the rotating output shaft 6, and thus a decrease inthe acceleration G of the vehicle until the engine speed NE reaches thetarget speed NEtrg. However, once the engine speed NE has reached to thetarget speed NEtrg, the majority of the output from the internalcombustion engine 16 is contributed to increasing the driving forcetransmitted to the rotating output shaft 6, so the acceleration G of thevehicle abruptly increases. Therefore, increasing the rate of increaseof the engine speed NE enables the acceleration G of the vehicle to bequickly increased to a predetermined acceleration, so the jerk J of thevehicle can be made large.

A routine for setting the parameters when the accelerator operationamount ACCP is substantially equal to the maximum amount according tothis example embodiment will now be described with reference to FIG. 4,which is a flowchart illustrating this routine. The routine shown inFIG. 4 is executed when the accelerator operation amount ACCP issubstantially equal to the maximum amount.

As shown in the drawing, in this routine it is first determined whetherthe power mode is selected (step S1). Here, if the power mode is notselected (i.e., NO in step S1), i.e., if the normal mode is selected,then the accelerator torque TL of the MG1 is set to a firstpredetermined value TL1 (step S2). This accelerator torque TL is torquethat is output from the MG1 and contributes to an increase of the rateof increase of the engine speed NE. The rate of increase of the enginespeed NE increases as the value of this accelerator torque TL becomeslarger. Next, a predetermined speed NEred is set to a value equal to thedifference of the target speed NEtrg minus a normal mode predeterminedvalue ΔNEnm1 (i.e., NEred=NEtrg−ΔNEnm1) (step S3). Here, thepredetermined speed NEred is a speed that defines the timing at which,while the engine speed NE is being increased to the target speed NEtrg,the rate of increase in the engine speed NE is reduced. Then this cycleof the routine ends.

The reason for reducing the rate of increase of the engine speed NE oncethe engine speed NE has been increased to the predetermined speed NEredthat is lower than the target speed NEtrg in this way will now bedescribed. If the engine speed NE is abruptly stopped from increasingafter being increased to the target speed NEtrg, the sudden change inacceleration of the engine speed NE will jolt parts of the internalcombustion engine 16, which may result in mechanical damage to theinternal combustion engine 16. Therefore, by reducing the rate ofincrease of the engine speed NE after the engine speed NE has beenincreased to the predetermined speed NEred that is lower than the targetspeed NEtrg, as described above, an abrupt change in the acceleration ofthe engine speed NE can be suppressed, thus inhibiting the internalcombustion engine 16 from being mechanically damaged.

On the other hand, if it is determined in step S1 that the power mode isselected (i.e., YES in step S1), then the accelerator torque TL of theMG1 is set to a second predetermined value TL2 that is larger than thefirst predetermined value TL1 (i.e., TL2>TL1) (step S4). As describedabove, the rate of increase of the engine speed NE increases as thevalue of the accelerator torque TL becomes larger. Next, thepredetermined speed NEred is set to a value equal to the difference ofthe target speed NEtrg minus a power mode predetermined value ΔNEpwrthat is less than normal mode predetermined value ΔNEnm1 (i.e.,ΔNEpwr<ΔNEnm1) (i.e., NEred=NEtrg−ΔNEpwr) (step S3). Then this cycle ofthe routine ends.

Setting the predetermined speed NEred larger when the power mode isselected than when the normal mode is selected in this way enables theengine speed NE to be increased to the target speed NEtrg more quicklycompared to when the predetermined speed NEred is the same for the powermode as it is for the normal mode. Therefore, the acceleration G of thevehicle can be increased more quickly to a predetermined acceleration.Also, the jerk J of the vehicle can be made even larger.

Next, the operation of this example embodiment will be described withreference to the timing charts shown in FIGS. 5A to 5E. Incidentally,FIG. 5A is a timing chart showing the shift in accelerator operationamount ACCP, FIG. 5B is a timing chart showing the shift in the throttleopening amount TA, FIG. 5C is a timing chart showing the shift in theaccelerator torque TL of the MG1, FIG. 5D is a timing chart showing theshift in the engine speed NE, and FIG. 5E is a timing chart showing theshift in acceleration G of the vehicle. Also, in the drawings, thebroken lines indicate shifts in the parameters when the normal mode isselected as the vehicle driving characteristic, and the solid linesindicate shifts the parameters when the power mode is selected as thevehicle driving characteristic.

As shown in the drawings, at timing t1, the accelerator operation amountACCP is 100% (i.e., the accelerator operation amount ACCP is equal tothe maximum amount and, more specifically, the accelerator pedal isfully depressed) (FIG. 5A), and consequently, the throttle openingamount TA is also 100% (i.e., the throttle opening amount TA is equal tothe maximum amount and, more specifically, the throttle valve is fullyopened) (FIG. 5B).

Here, when the normal mode is selected, as shown by the broken lines inthe drawings, the accelerator torque TL of the MG1 is set to the firstpredetermined value TL1 which is relatively small (FIG. 5C). Also, theengine speed NE increases as the throttle opening amount TA increases(FIG. 5D). Once the engine speed NE reaches a predetermined speedNEred1, which is relatively low, at timing t4, it then increases at aslower rate until it reaches the target speed NEtrg at timing 6 (FIG.5D). Also, from timing t1, the acceleration G of the vehicle graduallyincreases over time until maximum acceleration is reaches at timing t6(FIG. 5E). In this way, when the engine speed NE is increased to thetarget speed NEtrg when the normal mode is selected, the operation ofthe MG1 is controlled so that the driving force transmitted to therotating output shaft 6, of the output of the internal combustion engine16, increases.

On the other hand, when the power mode is selected, as shown by thesolid lines in the drawings, the accelerator torque TL of the MG1 is setto the second predetermined value TL2 which is relatively large (FIG.5C). Also, the engine speed NE increases as the throttle opening amountTA increases. Because the accelerator torque TL2 of the MG1 is largerthan it is when the normal mode is selected, the rate of increase of theengine speed NE is greater than it is when the normal mode is selected(FIG. 5D). Therefore, the engine speed NE reaches a predetermined speedNEred2, which is relatively high, at timing t2. After that, the enginespeed NE increases at a slower rate until it reaches the target speedNEtrg at timing t3 (FIG. 5D). Also, from timing t1, the acceleration Gof the vehicle temporarily increases, but then gradually decreases overtime until timing t3 when the engine speed NE reaches the target speedNEtrg. In this way, when the power mode is selected, the operation ofthe MG1 is controlled so that the driving force transmitted to therotating output shaft 6, of the output of the internal combustion engine16, decreases when the engine speed NE is increased to the target speedNEtrg. Then after timing t3, the acceleration G of the vehicle abruptlyincreases until maximum acceleration is reached at timing t5 (FIG. 5E).Here, the period from timing t3 to timing t5 is when the jerk J of thevehicle is greatest.

The operation and effects described below are able to be obtained withthe control apparatus for a vehicle according to the example embodimentdescribed above.

(1) The provided MG1 that steplessly changes speed ratios when therotational driving force of the crankshaft 16 a is transmitted to therotating output shaft 6. Also, when the engine speed NE is increased tothe target speed NEtrg when the accelerator operation amount ACCP issubstantially equal to the maximum amount, the HV-ECU 30 executescontrol to operate the MG1 such that the rate of increase of the enginespeed NE becomes greater when the power mode is selected than it doeswhen the normal mode is selected. This kind of control enables theacceleration G of the vehicle to quickly be increased to a predeterminedacceleration. Also, the rate of increase when the acceleration G of thevehicle is increased, or so-called jerk J, can be made large. Therefore,a greater feeling of acceleration can be obtained when the power mode isselected than when the normal mode is selected, even if the requiredoutput of the internal combustion engine 16 is the same when the powermode is selected as it is when the normal mode is selected.

(2) When the engine speed NE is increased to the target speed NEtrg whenthe power mode is selected, control is executed to operate the MG1 suchthat the driving force transmitted to the rotating output shaft 6, ofthe output of the internal combustion engine 16, decreases. When theengine speed NE is increased to the target speed NEtrg when the powermode is selected, the output of the internal combustion engine 16 thatcontributes to an increase of the engine speed NE increases by theamount that the driving force transmitted to the rotating output shaft6, of the output of the internal combustion engine 16, decreases, whichenables the engine speed NE to be increased to the target speed NEtrgmore quickly. Therefore, the acceleration G of the vehicle can bequickly increased to a predetermined acceleration, and the jerk J of thevehicle can be made large.

(3) After the engine speed NE has been increased to the predeterminedspeed NEred, which is lower than the target speed NEtrg, the rate ofincrease of the engine speed NE is reduced. Also, the predeterminedspeed NEred is set higher when the power mode is selected than it iswhen the normal mode is selected. This kind of control enables theengine speed NE to be quickly increased to the target speed NEtrg.Therefore, the acceleration G of the vehicle can be quickly increased toa predetermined acceleration, and the jerk J of the vehicle can be madelarge.

(4) The provided hybrid power system 2 distributes a portion of theoutput from the internal combustion engine 16 to the rotating outputshaft 6, generates electric power by distributing the rest of the outputfrom the internal combustion engine 16 to the MG1, charges the powerstorage device 26 with that generated electric power, and transmitspower to the rotating output shaft 6 using the MG2 that is driven by theelectric power from the MG1 and/or the electric power from the powerstorage device 26. Also, the speed ratio when the rotation driving forceof the crankshaft 16 a is transmitted to the rotating output shaft 6 issteplessly changed by controlling the operation of the MG1. Therefore,the speed ratio when the rotation driving force of the crankshaft 16 ais transmitted to the rotating output shaft 6 can be easily changed.

Incidentally, the control apparatus for a vehicle according to theinvention is not limited to the structure described in the foregoingexample embodiment, but may be modified appropriately. For example, theinvention may also be carried out as follows. In the example embodimentdescribed above, the internal combustion engine is described as agasoline engine, but it may also be a diesel engine.

The example embodiment described above describes a vehicle provided withthe hybrid power system 2 that distributes a portion of the output fromthe internal combustion engine 16 to the rotating output shaft 6,generates electric power by distributing the rest of the output from theinternal combustion engine 16 to the MG1, charges the power storagedevice 26 with the generated electric power, and transmits power to therotating output shaft 6 using the MG2 that is driven by the electricpower from the MG1 and/or the electric power from the power storagedevice 26. That is, the example embodiment describes a vehicle providedwith the MG1 and the planetary gear set 20 as the continuously variabletransmission mechanism that steplessly changes speed ratios when therotational driving force of the crankshaft 16 a is transmitted to therotating output shaft 6. However, the continuously variable transmissionmechanism according to the invention is not limited to being this kindof electric continuously variable transmission mechanism. Alternatively,a mechanical continuously variable transmission mechanism may beapplied. In this case, the speed ratio when the rotational driving forceof the crankshaft 16 a is transmitted to the rotating output shaft 6 maybe steplessly changed by controlling the effective radius of a pulleythat forms part of the continuously variable transmission mechanism.

In the example embodiment described above, the rate of increase of theengine speed NE is reduced after the engine speed NE has been increasedto the predetermined speed NEred which is lower than the target speedNEtrg. Employing this kind of control mode is preferable for suppressinga sudden change in the acceleration of the engine speed NE, and thussuppressing mechanical damage to the internal combustion engine 16.However, the control of the engine speed NE according to the inventionis not limited to this. That is, this kind of control mode does not haveto be employed.

In the example embodiment described above, when the engine speed NE isincreased to the target speed NEtrg when the normal mode is selected,the continuously variable transmission mechanism is controlled such thatthe driving force transmitted to the rotating output shaft 6, of theoutput from the internal combustion engine 16, increases, i.e., suchthat the acceleration G of the vehicle increases. However, the controlof the engine speed NE when the normal mode is selected is not limitedto this. As long as the rate of increase when the engine speed NE isincreased to the target speed NEtrg is made smaller when the normal modeis selected than it is when the power mode is selected, the continuouslyvariable transmission mechanism may also be controlled such that thedriving force transmitted to the rotating output shaft 6, of the outputfrom the internal combustion engine 16, decreases.

In the example embodiment described above, when the engine speed NE isincreased to the target speed NEtrg when the power mode is selected, thecontinuously variable transmission mechanism is controlled such that thedriving force transmitted to the rotating output shaft 6, of the outputfrom the internal combustion engine 16, decreases, i.e., such that theacceleration. G of the vehicle decreases. However, the control of theengine speed NE when the power mode is selected is not limited to this.As long as the rate of increase when the engine speed NE is increased tothe target speed NEtrg is greater when the power mode is selected thanit is when the normal mode is selected, the continuously variabletransmission mechanism may also be controlled such that the drivingforce transmitted to the rotating output shaft 6, of the output from theinternal combustion engine 16, is increased.

In the example embodiment described above, when the engine speed NE isincreased to the target speed NEtrg when the accelerator operationamount ACCP is substantially equal to the maximum amount, thecontinuously variable transmission mechanism is controlled such that therate of increase of the engine speed NE becomes larger when the powermode is selected than it does when the normal mode is selected. However,the condition for executing this control of the invention is notnecessarily limited to the accelerator operation amount ACCP beingsubstantially equal to the maximum amount.

That is, when the rotation speed of the engine output shaft is increasedto the target rotation speed and the required output of the internalcombustion engine is the same when the power mode is selected as it iswhen the normal mode is selected, the continuously variable transmissionmechanism may be controlled such that the rate of increase of therotation speed of the engine output shaft becomes greater when the powermode is selected than it does when the normal mode is selected.

The invention claimed is:
 1. A control apparatus for a vehicle in whichrotational driving force of an engine output shaft that is an outputshaft of an internal combustion engine is transmitted to a driving wheelvia a rotating output shaft, and which has a normal mode and a powermode as vehicle driving characteristics, the control apparatuscomprising: a continuously variable transmission mechanism thatsteplessly changes a speed ratio when the rotational driving force ofthe engine output shaft is transmitted to the rotating output shaft, athrottle valve of the internal combustion engine being fully open whenan accelerator operation amount is equal to the maximum amount, and acontrol portion that, when the accelerator operation amount is equal tothe maximum amount, in a case where the power mode is selected, when arotation speed of the engine output shaft is increased to a targetrotation speed, controls the continuously variable transmissionmechanism such that the driving force transmitted to the rotating outputshaft, of the output from the internal combustion engine, decreases, sothat the rate of increase in the rotation speed of the engine outputshaft is greater than that in a case where the normal mode is selected.2. The control apparatus for the vehicle according to claim 1, whereinthe control portion, in the case where the normal mode is selected, whenthe rotation speed of the engine output shaft is increased to the targetrotation speed, controls the continuously variable transmissionmechanism such that the driving force transmitted to the rotating outputshaft, of the output from the internal combustion engine, increases. 3.The control apparatus for the vehicle according to claim 1 wherein:after the rotation speed of the engine output shaft has been increasedto a predetermined rotation speed that is lower than the target rotationspeed, the control portion makes the rate of increase in the rotationspeed of the engine output shaft lower than the rate of increase in therotation speed of the engine output shaft when the rotation speed of theengine output shaft is equal to or lower than the predetermined rotationspeed; and the control portion sets the predetermined rotation speedhigher in the case where the power mode is selected than in the casewhere the normal mode is selected.
 4. The control apparatus for thevehicle according to claim 1, further comprising: a hybrid power systemthat distributes a portion of the output from the internal combustionengine to the rotating output shaft, charges a power storage device withelectric power generated by distributing the rest of the output from theinternal combustion to a generator, and transmits power to the rotatingoutput shaft using an electric motor that is driven by one or both ofthe electric power from the generator and the electric power from thepower storage device, wherein the continuously variable transmissionmechanism steplessly changes the speed ratio when the rotational drivingforce of the engine output shaft is transmitted to the rotating outputshaft, by control of an operation of the generator.